Investigating the effect of copper sulphate on the rate of reaction

Investigating the effect of copper sulphate on the rate of reaction.

Introduction

Enzymes are proteins produced by living cells; they act as a catalyst in biochemical reactions. The enzyme may catalyse a reaction in which the substrate molecule is split into separate molecules. Alternately it may cause the joining of two molecules. There main properties which are common with other catalysts are they remain chemically unaltered by the reaction they catalyse, they are not used up in any one reaction, they do not make reactions occur which usually would not happen and do not alter the amount of product formed.

Enzymes are globular proteins (these are long chains of amino acids held together by peptide bonds) and are coiled into precise three-dimensional shape with hydrophilic side chains known as R groups to ensure that they are soluble. The most unique property is the need for an active site to mirror that precisely of a particular substrate molecule (this has become know as the lock and key model). This site allows a substrate to bond to the enzyme to form an enzyme substrate complex the active site is usually in the form of a cleft or depression. Temporary chemical bonds form between the substrate and some the R groups of the enzymes amino acids. Other groups of atoms within the active site speed up the chemical reaction of a substrate. Most enzyme reactions involve two or three such catalytic groups. The product then leaves the active site, this possess can be extremely rapid.

The rate of enzyme reaction depends mainly on three factors the concentration of enzyme, the pH level and the temperature of the reaction. Heating the reactants can increase all chemical reactions. Heat energy is transferred to the reactants insuring more successful collisions (or an increased rate in an enzyme-catalysed reaction). The substrate and enzyme collide with more energy so more of those collisions result in the formation of product. But above a certain temperature namely 40° heat also causes a change in the shape of protein molecules, this is known as denaturisation. Denaturisation occurs when weak bond which stabilise a proteins ...

This is a preview of the whole essay

The level of pH as well as tempreture can denature proteins. The lower the pH level the higher the hydrogen ion concentration. Hydrogen ion can interact with the amino acids R groups, affecting the way in which they bond and therefore the 3D structure of an enzyme.

Enzyme and substrate concentration are a major factor of reaction rate. The rate of an enzyme-controlled reaction depends mainly on the amount of successful collisions. If enzyme molecules are added there will be more successful collisions will occur and the rate of reaction will increase. Therefore as long as there is an excess of substrate the rate of an enzyme-catalysed reaction is directly proportional to the amount of enzyme. The rate of reaction is also affected by the amount substrate as long as the amount of enzyme is fixed. An increase in the substrate concentration increases the amount of successful collisions so the rate of reaction is faster, however at higher substrate concentrations the active site of every enzyme is being occupied at any one moment. Any added substrate will have to wait until an active site is empty thus lowering the rate of reaction.

One other factor that can affect the rate of reaction is inhibitors. Inhibitors are substances that reduce the rate of reaction. They do this by binding to the enzyme forming an enzyme-inhibitor complex. If the complex

can dissociate the processes is reversible if the complex cannot dissociate the process is irreversible. There are two types of inhibitor competitive and non-competitive. Competitive inhibitors bond with the active site of an enzyme, thereby stopping substrate molecules attaching. Increasing the concentration of substrae can usually reduce a competitive inhibitors affect, since the amount probability for an enzyme-substrate complex to be formed is grater then an enzyme-inhibitor complex.

A non-competitive inhibitor combines with another part of an enzyme other then the active site in doing so it may change the shape an enzyme so that the substrate may no longer bond with the enzyme.

Task